The Efficacy and Neurotoxicity of Dexmedetomidine Administered Via the Epidural Route

Background: alpha(2)-Adrenoceptor agonists administered into the intrathecal and epidural space have been found to be effective in the treatment of chronic pain. Moreover, it was shown that they increase the analgesic effects of local anaesthetics and provide sedation, anxiolysis and haemodynamic stability. Dexmedetomidine, a potent and highly selective alpha(2)-adrenoceptor agonist, is in current clinical use, particularly in the intensive care unit. Our aim was to investigate whether dexmedetomidine produced motor and sensory blockade and neurotoxic effects when administrated via the epidural catheter in rabbits.

Methods: Twenty-one New Zealand white rabbits were included in the study. Animals were randomized into three groups. In Group L: lidocaine (2%), in Group LD: lidocaine (2%) + dexmedetomidine (5 microg) and in Group D: dexmedetomidine (10 microg) were administered by epidural catheter. Motor and sensory blockade were evaluated. After the evaluation of block, the animals were euthanized and their spinal cords removed for neuropathological evaluations.

Results: Motor and sensory blockade were lower in Group D than in Group L and Group LD (P < 0.01). Although there were no differences between the groups for ischaemia of the medulla spinalis, evidence of demyelinization of the oligodendrocytes in the white matter in Group D was significantly higher than in Group L (P = 0.035).

Conclusions: We observed that dexmedetomidine does not have motor and sensory effects, but it may have a harmful effect on the myelin sheath when administered via the epidural route.